package com.hmdp.utils;

import cn.hutool.core.lang.UUID;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.data.redis.core.script.RedisScript;

import java.util.Collections;
import java.util.concurrent.TimeUnit;

public class SimpleRedisLock implements ILock{

    private String name;
    private StringRedisTemplate stringRedisTemplate;


    public SimpleRedisLock(String name, StringRedisTemplate stringRedisTemplate) {
        this.name = name;
        this.stringRedisTemplate = stringRedisTemplate;
    }

    //锁的key前缀
    private static final String KEY_PREFIX = "lock:";

    //锁value值的线程的前缀
    private static final String ID_PREFIX = UUID.fastUUID().toString(true) + "-";
    private static final DefaultRedisScript<Long> UNLOCK_SCRIPT;

    static {
        UNLOCK_SCRIPT = new DefaultRedisScript<>();
        UNLOCK_SCRIPT.setLocation(new ClassPathResource("unlock.lua"));
        UNLOCK_SCRIPT.setResultType(Long.class);
    }

    @Override
    public boolean tryLock(long timeoutSec) {

        String threadId = ID_PREFIX + Thread.currentThread().getId();

        //setIfAbsent() 如果不存在  下面这句相当于set lock thread1 nx(互斥) EX(超时时间) 10
        Boolean success = stringRedisTemplate.opsForValue().
                setIfAbsent(KEY_PREFIX + name, threadId, timeoutSec, TimeUnit.SECONDS);
        return success.TRUE.equals(success);
    }

    @Override
    public void unlock() {
        stringRedisTemplate.execute(UNLOCK_SCRIPT,
                Collections.singletonList(KEY_PREFIX + name),
                ID_PREFIX + Thread.currentThread().getId());
    }

    //下面的代码会出现原子性问题
    /*@Override
    public void unlock() {

        //获取线程标识
        String threadId = ID_PREFIX + Thread.currentThread().getId();

        //判断是否一致
        String id = stringRedisTemplate.opsForValue().get(KEY_PREFIX + name);

        if (threadId.equals(id)) {

            //释放锁
            stringRedisTemplate.delete(KEY_PREFIX + name);
        }

    }*/
}
